Abstract: A fuse assembly having a displaceable pin assembly secured within a cap bore of an end cap of the fuse assembly. The displaceable pin assembly can include a plunger that is selectively displaceable along an axis that is non-parallel to a central longitudinal axis of the first end cap. The plunger can be selectively displaceable between an extended position at which at least a first end of the plunger is outwardly positioned away from an outer surface of the first end cap, and a recessed position at which the first end of the plunger is recessed within, or generally aligned with the outer surface of, the first end cap. The displaceable pin assembly can also include a biasing element that can bias the plunger to the extended position, and a support body that can house at least a portion of the plunger and be securely coupled to the cap bore.

Abstract: A pyrotechnic circuit breaker includes a housing with at least one cutting chamber, at least one electrical conductor, at least one punch designed to section the at least one electrical conductor, at least one pyrotechnical actuator, and an insert moulded on the at least one electrical conductor. The housing includes a first housing part and a second housing part with at least one sealing means between the insert and one of the first housing part and/or of the second housing part in order to ensure a seal of this at least one cutting chamber.

Abstract: Examples of an apparatus and method are disclosed herein. In an example of the method, the performance of an ejection device that dispenses a composition is measured, information representative of the measured performance of the ejection device is generated, and the information representative of the measured performance of the ejection device is recorded so that the information is visually perceptible.

Abstract: A release apparatus includes a coiled restraining wire with each end attached to a corresponding fuse wire. The fuse wires are supplied with respective actuation electric currents by respective independent current sources. Flow of actuation current through a fuse wire causes that fuse wire to break; breakage of either one or both fuse wires allows the restraining wire to partially uncoil and allow the release apparatus to transition from a retained condition to a released condition, by allowing disengagement of retention members from a release member that can then move out of the release apparatus. The release apparatus can be employed to attach a deployable component to a satellite or spacecraft, and can be readily repaired, refurbished or reset for repetitive ground testing.

Abstract: A release apparatus includes a coiled restraining wire with at least one end attached to a fuse wire. Actuation current through the fuse wire causes it to break; breakage of the fuse wire allows the restraining wire to partially uncoil and allow the release apparatus to transition from a retained condition to a released condition, by allowing disengagement a sleeve from retention members and disengagement of retention members from a release member that can then move out of the release apparatus. The sleeve isolates the restraining wire and fuse wire from load forces on the release member. Rolling bearings within the sleeve against the retention members reduces resistance to disengagement of the sleeve. The release apparatus can be employed to attach a deployable component to a satellite or spacecraft, and can be readily repaired, refurbished or reset for repetitive ground testing.

Abstract: The present disclosure includes an insert for a fuse structure. In one approach, a fuse, includes a housing having a cavity, a fuse element disposed within the cavity, a plurality of terminals extending out of the housing and electrically connected to the fuse element, and an insert disposed in the cavity, the insert including a pin extending through an opening of the housing. In some approaches, the insert includes a separating wall defining first and second cavities of the insert.

Abstract: A hold-down release apparatus includes a housing, a reciprocating retention member, a release member, bias member(s), and a fuse wire. The retention member moves between retention and release positions and is biased toward the release position. With the retention member in the release position, the release member can move out of the housing; with the retention member in the retention position, the retention member obstructs the release member from moving out of the housing. The fuse wire obstructs movement of the retention member to the release position and holds the retention member in the retention position against the bias force. With an actuation current flowing through the fuse wire, the bias force breaks the fuse wire, allowing the retention member to move to the release position in response to the bias force, and the release member to move out of the housing.

Abstract: An embodiment of an in-line fuse holder has been disclosed. The fuse holder includes a first terminal and a second terminal configured to cooperate with the first terminal in retaining a fuse between the first terminal and the second terminal, wherein each of the first and second terminals has a sidewall that defines a fuse-receiving socket, the sidewall having a plurality of apertures circumferentially spaced about the socket.

Abstract: A fuse including a fuse housing having first and second electrical terminals, a movable partition made from an electrically conductive material movably disposed within the fuse housing, a fusible structure connected between the first electrical terminal and the movable partition, a conductor connected between the movable partition and the second electrical terminal, a biasing element acting on the movable partition to maintain the fusible structure in tension and for moving the movable partition upon melting of the fusible structure and an indicator connected between the movable partition and the second electrical terminal.

Abstract: A multiple fused junction with blown fuse indication which generally includes a main body, a fuse connected to the main body and a switch disposed within the main body. The main body has multiple cable ports extending outwardly therefrom. At least one of the ports is adapted for electrical connection with a feeder cable and another of the ports is adapted to receive a fuse. The fuse is removably connected to the fuse port of the main body and has an indicator rod movably disposed therein, which protrudes from an axial end of the fuse into the main body upon electrical interruption of the fuse. The switch is disposed within the main body adjacent the fuse port and is activated by the indicator rod of the fuse upon protrusion of the rod from the fuse to provide indication of electrical interruption of the fuse.

Abstract: A fuse state indicator includes an extension member, a secondary fuse link coupled to the extension member, and a contact pin configured to engage a first terminal element of a fuse. An end of the secondary fuse link is wrapped around the pin and establishes an electrical connection thereto.

Abstract: A cable limiter includes a main body having a cavity. The cavity of the main body is structured to receive a replaceable fusible element. An annunciator is housed by the main body. The annunciator is structured to annunciate status of the replaceable fusible element.

Abstract: An apparatus for indicating the proper seating of a high voltage fuse in its mounting assembly in connection with electrical switchgear utlilizes a spring loaded flag positioned adjacent a latching protrusion for engagement by the latch of the mounting assembly such that the flag is moved from an obscured position to an visible position only when the latch is in its affirmatively locked position.

Abstract: A fuse that allows for additional connections to be made. The fuse includes a housing with a body and a pair of sides. A pair of terminals may be mounted to and extend from each of the sides. At least one fusible link may be mounted inside the housing to prevent excessive current flow. A terminal is connected to each end of each of the fusible link. A light emitting diode can be mounted to the housing to indicate a positive terminal.

Abstract: The impact signaling system (9) is used in a high-voltage protective device and has a housing (13), a spring (16) which is arranged in the housing (13) and has a moveable end, an actuator (17) which can be passed out of the housing (13) and interacts with the moveable end of the spring (16), a high-resistance resistor wire (12) which is connected in parallel with a fusible wire of the protective device, and a holder which absorbs the prestress of the spring (16). The holder contains a section of the high-resistance resistor wire (12) which is in the form of a winding (18) and is passed at least once around the moveable end of the spring (16) in order to form the prestress, and which is at least partially in thermally conductive contact with the material of the activator (20). Above a limit temperature, the activator (20) lifts, for example by destruction of the winding (18) or by melting through, the holder and activates the impact signaling system (9) by reducing the load on the spring (16).

Abstract: A fuse is provided that is suitable for operation in unusual environments and includes an operation indicator that is simple and reliable. A movable arcing tube is released during operation. As the arcing tube moves outside the fuse assembly, a latching spring moves into a receiving groove in the arcing tube to retain the arcing tube in the external operated position.

Abstract: The impact signaling system (9) is used in a high-voltage protective device and has a housing (13), a spring (16) which is arranged in the housing (13) and has a moveable end, an actuator (17) which can be passed out of the housing (13) and interacts with the moveable end of the spring (16), a high-resistance resistor wire (12) which is connected in parallel with a fusible wire of the protective device, and a holder which absorbs the prestress of the spring (16). The holder contains a section of the high-resistance resistor wire (12) which is in the form of a winding (18) and is passed at least once around the moveable end of the spring (16) in order to form the prestress, and which is at least partially in thermally conductive contact with the material of the activator (20). Above a limit temperature, the activator (20) lifts, for example by destruction of the winding (18) or by melting through, the holder and activates the impact signaling system (9) by reducing the load on the spring (16).

Abstract: A fuse is provided that is suitable for operation in unusual environments and includes an operation indicator that is simple and reliable. A movable arcing tube is released during operation. As the arcing tube moves outside the fuse assembly, a latching spring moves into a receiving groove in the arcing tube to retain the arcing tube in the external operated position.

Abstract: A fuse state indicator includes a fuse casing having a transparent lens, a combustible substance disposed adjacent the lens, and a base layer disposed adjacent the combustible substance and having a contrasting color relative to the combustible substance. A secondary fuse indicating circuit is electrically connected to a main fuse circuit in parallel with a main fuse link, and includes a secondary fuse wire link which is disposed adjacent the combustible substance. Heat created upon vaporization of the secondary fuse link ignites the combustible substance and reveals the base layer through the lens after combustion, thereby indicating a state of the fuse as operable or inoperable by the color visible through the lens. Combustion may be assisted with an energetic chemical compound applied to secondary fuse wire link and combustible substance.

Abstract: An electrostatic discharge ground path for a fuse installable in a fuse holder includes an area of metallization on at least one insulating surface of the fuse extending from an exposed surface of the fuse to a contact area within the fuse holder.

Abstract: A fuse for interfacing electrical current with electronic components and for shielding the electronic components from potentially damaging electrostatic discharge. The fuse includes a fuse body having an edge and first and second electrical contacts. A fuse indicator is connected to one electrical contact and a fuse element extends between the indicator and the other contact for providing a conduit for operating current to reach the interfaced electronic components. A window is disposed on the edge of the fuse body and positioned over the fuse indicator. Sealant is disposed between the window edge and the fuse body edge to prevent the accumulation of air therebetween and, thereby, preventing such accumulated air from functioning as a transmission medium through which an electrostatic discharge can travel and reach the electronic components.

Abstract: A pin indicating fuse construction incorporates a protective shield member that isolates an indicator assembly from a main-fuse link. By use of the inventive protective shield, arc-quenching filler may be excluded, resulting in a less-costly, more reliable fuse construction. The main fuse link is arranged within the fuse in such a manner so as to minimize potential interference with the actuator assembly during activation of the indicator assembly.

Abstract: Limiters for protection against fault currents in electrical distribution networks the limiter having externally visible indicator for indicating that a limiter element has fused and which visible indicator may be reset and reused after a fused limiter is replaced.

Abstract: A striker pin device for providing a visual indication of an operated condition of an associated fuse, comprising a tubular housing coaxially arranged within the fuse with an end of the housing in contact with an end of the fuse. The tubular housing has a closure structure comprised of a one-piece integrally formed closure member having a projection protruding out of the housing and an opened end with a cavity. A piston with a central projection received in the opened end of the closure member forms a gas tight enclosure containing pyrotechnic material. An ignition element is attached to a brass pin which extends through the projection of the closure member and is connected to a tubular terminal or electrical conductor member which is attached to a high resistance pilot wire, which is stretched through the fuse.

Abstract: An externally mounted blown fuse indicator including a housing, a spring-biased plunger, a tungsten restraining wire, two terminals, and a cover, the plunger having a meltable region that is heated by the restraining wire and melts to release the plunger when the fuse blows, the spring engaging a midsection of the plunger, the housing carrying tabs at its ends for engagement with a switch to be activated by the plunger, the spring-biased plunger having greater than 3 ounces force at an extension of 0.11".

Abstract: Fuse cartridge, of the type comprising, a striking element (8) retained against elastic means (7) by a conductive wire (6) connected between the connection heads (2) in parallel with at least one meltable element (5) so as to melt with the latter under the effect of an accidental overintensity, a micro-switch (9) whose knob (12) is intended to be actuated by said striking element to supply an alarm circuit in the case of melting of element (5), characterized in that, between the knob (12) and the striking element (8) there is interposed a rocking lever (13) profiled in the manner of a cam in order to give the micro-switch (9) two stable positions of functioning, whatever its inner mechanism.

Abstract: The blown fuse indicator is mounted to one of the opposed ferrules of a fuse and ejects a streamer therefrom in response to a blown or open fuse condition. The streamer is a strip of vinyl which is secured at one end to a plunger held within a housing mounted on one of the ferrules, and at its other end to a container which is ejected from the housing by the plunger in response to a fuse opening whereby the streamer unfurls to indicate the fuse is blown and open.

Abstract: An electric fuse constructed of a subassembly including a blown-fuse preassembly. The preassembly includes a stationary structure including an indicator housing having a chamber therein, an indicator pin mounted in the chamber for movement from a nonindicating position to an indicating position, an indicator spring mounted between the indicator housing and the indicator pin so as to bias the indicator pin from the nonindicating position to the indicating position, and a flexible indicator restraining wire having a first portion engaging the pin for restraint and, on respective sides of the first portion, second and third portions extending out of the indicator housing, the wire being in tension against force provided by the indicator spring to the indicator pin, the indicator wire restraining the pin in the nonindicating position and maintaining the spring cocked, the second and third portions being secured under tension by rigid bonding to the stationary structure.

Abstract: This invention relates to an operation-indicating device for fuse cartridges for electrical protection, of the type comprising a plunger formed by a pusher element which is retained against a resilient actuating member by a secondary fuse wire connected in parallel with the wire or wires or fusible elements of the cartridge, characterized in that the base of the plunger cooperates with the conventional portion of the reduced section of the secondary wire, and an intermediate piece is in contact with the wire on either of said portion which is arranged so as to behave in non-conductive manner with respect to low-voltage current which passes through this wire and in conductive manner when the reduced section is fused so that the high-voltage current is transmitted to the two parts of the secondary wire disposed on either side of the portion of reduced section.

Abstract: A spring loaded blown fuse indicator is provided that is adapted to be mounted directly on the side of an electric fuse in parallel with the fuse current path.The indicator provides an indicating pin that extends perpendicular to the longitudinal axis of the fuse. The indicator body comprises two identical molded halves which facilitate assembly and allow the indicator restraining wire to be readily encapsulated in an arc-quenching epoxy adhesive.

Abstract: A current limiting fuse with an indicator characterized by a generally tubular, electrically insulating casing having a pair of tubular terminal members at opposite ends of the casing. A fusible element extends between the terminal members and through the casing. An indicator plunger extends from one end terminal member and is movable between a retracted and extended positions and is biased in the extended position. A restraining wire extending between the other end terminal member and the indicator plunger. The wire having a smaller diameter portion in the casing. An electrically conductive grease disposed between the plunger and the tubular terminal member.

Abstract: An HRC-fuse as an insulating body surrounding a main fusible conductor and an auxiliary fusible conductor connected to a spring biased impact pin. A conductive cap serving as a terminal for the fusible conductors is arranged on the insulating body and is provided with an outlet opening opposite the impact pin. A tripping hollow pin or sleeve coaxially surrounds at least a part of the impact pin and passes through the outlet opening. A bimetal release pawl is arranged in the one cap parallel to the pin and being electrically connected to the fusible conductors. The pawl engages a rest on the tripping sleeve to counteract a biasing spring. The impact pin and the tripping sleeve are triggered independently one from the other either by a short-circuit current melting the auxiliary conductor, or by an overload which heats up the bimetal release and triggers the sleeve. Both the tripping sleeve and the impact pin act on a load interruptor arranged opposite the outlet opening.

Abstract: A fuse (12) for protecting a circuit and comprising a tube (14) of insulating material having an inner wall surface (16) and an outer wall surface (18) so as to form a fuse housing. The fuse includes two opposite axial ends (20) and (22), and a first (24) and a second conductive fuse terminal (26) are secured to the tube adjacent each of those opposite axial ends, respectively. Serially-located elements (28) are disposed within the fuse housing and provide electrical continuity between the first fuse terminal and the second fuse terminal. The elements comprise stressed spring means (30) and resistor means (32), with the spring means having a proximate end (40) secured to the fuse adjacent the first fuse terminal and a distal end (41) secured through a meltable junction (34) to the resistor means.

Abstract: An elongated fuse housing includes a fusible wire longitudinally extended and coaxially mounted within a housing having end terminals. A spring indicator unit is secured to one end and includes a relatively large diameter loosely wound section forming a helical compression spring in combination with an integral, coaxial and tightly wound elongated indicator coil which extends axially of the spring. The spring/indicator unit is located within the housing with the coil spring held compressed by the fusible wire. The one end terminal includes an opening aligned with the wire-wound indicator coil. Disruption of the fusible wire releases the coil spring which expands within the housing to rapidly separate the fuse wire and simultaneously move the elongated wire-wound indicator coil through the opening, thereby indicating operation of the fuse.

Abstract: A brake and operation indicator for a movable contact of a switch, the movable contact being rapidly moved by ignition of a power cartridge to open the switch. A thin-walled sleeve is positioned conformally about a movable pin, a portion of which is lightly held in a bore of an end member of a housing for the switch. The sleeve is shorter than the distance between a head on the pin and the end member. The bore is normally closed by a thin membrane. When the contact is moved, it ultimately abuts the head, moving the pin through the membrane to a position beyond the end member where a portion of the pin is visible. Movement of the pin also collapses the sleeve between the head and the end member in accordion-like fashion to dissipate the kinetic energy of and stop the contact. The presence of the pin within the sleeve renders the collapse controlled, uniform, and efficient. The visible portion of the pin informs that the switch is open.

Abstract: An energy-limited fuse having a number of fuse elements spirally wrapped about a spider formed from a number of insulating plates, the fuse elements being supported in a parallel spaced relation at a distance sufficient for each element to operate independently and a striker pin assembly independently mounted in said fuse after said spider assembly has been mounted in said fuse, said striker pin assembly including a vaporizable wire for holding the striker pin in said striker pin assembly until the fuse elements are vaporized.

Abstract: An electric fuse is provided with a blown fuse indicator mounted on a lateral wall of the fuse. One of the end terminals of the fuse is provided with a first opening therein in a surface which faces the interior of the fuse casing. The same end terminal is provided with a second opening therein which is in a peripheral surface of the terminal and which lies in a plane which is substantially parallel to the longitudinal axis of the fuse casing. The end terminal is further provided with an internal passageway therein which communicates the first and second openings. The fuse casing is provided with an opening therein which is in axial alignment with the second opening in the end terminal.A spring loaded blown fuse indicator is mounted through the opening in the fuse casing and is fixedly and conductively engaged with at least a portion of the end terminal passageway.

Abstract: An alarm indicator fuse (1) for large current and high temperature applications. The fuse assembly comprises apparatus (16, 121, 162) slidably engaging alarm indicator apparatus (14, 15) coupled between one conducting member (12) and a fuse element (13) electrically connected to another conducting member (11) to electrically couple the fuse element to the one conducting member and enable release of the alarm indicator apparatus upon opening of the fuse element. The electrically coupling and release enabling apparatus shortens the current path of the fuse between the electrical conducting members to increase the current capacity and improve the temperature characteristics of the fuse.

Abstract: This invention relates to electric fuses meeting the requirements of Underwriter's RK1 classification. It includes a high-current interrupter in the form of a fusible element having serially arranged points of reduced cross-section and a low-current interrupter in the form of a plunger soldered to the high-current interrupter. The plunger is spring biased, and when the solder joint softens, the plunger separates under the action of the spring from the fusible element leaving a large gap between them. The separation of the plunger from the fusible element is allowed to be particularly large on account of the fact that the plunger may be allowed to move into a special fuse cap, known as a cap having a rejection feature as described, for instance, in U.S. Pat. No. 2,943,295 to V. N. Stewart; June 28 1960 for REJECTION TYPE FUSE CLIP and in many other patents.

Abstract: A heat sensitive telephone protector module of a type having visual indicator means to indicate the actuation of heat sensitive means upon the occurrence of excessive current flow. The module includes dual heat sensitive units for protecting the tip and ring circuits of an individual subscriber pair, and a single indicator unit which is outwardly projected from the module housing by action of either heat sensitive element.

Abstract: A blown fuse indicator for an electric fuse having a tubular casing of insulating material, a pair of terminal caps mounted on the ends of the casing to close the ends thereof, a fuse link conductively interconnecting the terminal caps and an arc quenching filler material filling the casing to embed the fuse link, the fuse indicator including an indicator housing supported by one of the end caps, a pin type indicator positioned within the housing and biased outwardly from the housing to pierce a plate provided at the outer end of the indicator housing and a pair of members formed of a non-conductive material and having a plurality of corresponding opening in the form of holes or notches with a fuseable wire threaded through the openings to prevent relative movement between the members, one of the members being supported by the housing and the other of the members being connected to the indicator, on fusing of the wire the member connected to the indicator being released allowing the indicator to move to the i

Abstract: A fuse striker affords a visual or other indication of an operated condition of an associated fuse and is mounted within the fuse and comprises a housing structure coaxially arranged within the fuse with an end of the housing in contact with an end of the fuse, closure structure for the opposite end of the striker housing and comprising mating half sections with a longitudinal groove formed in at least one complementary surface through which an elongated high resistance ignition element extends and which is in shunt with the fusible elements of the fuse so as to contact with pyrotechnic material interposed between the closure means and a cup like piston element having an outwardly flared lip portion whereby ignition of the pyrotechnic element drives the piston toward the opposite end of the housing so as to thrust a striker pin mounted therein through the fuse cap so as to afford a visual indication of the operated condition of the fuse, the pyrotechnic material being ignited upon rupture of the fusible eleme

Abstract: A fuse for elevated circuit voltages having a blown fuse indicator. The fuse is characterized by its great simplicity of design. Virtually all its components, or constituent parts, form a sub-assembly capable of being inserted as a unit into the fuse tube or casing. One terminal of the fuse is formed by a plug contact that defines a heating chamber for heating one end of the restraining wire for the blown fuse indicator above all other points thereof. The other terminal of the fuse is formed by a ferrule, or terminal cap, conductively connected to a perforated metal disk, or metal plate, arranged immediately adjacent thereto. That disk or plate performs four functions, namely (1) to help support insulating rods around which the fusible element is helically wound, (2) to form one of the terminals of the fusible element and of the restraining wire for the blown fuse indicator, and (3) to provide a large aperture through which the fuse is easily filled with arc-quenching filler.

Abstract: In a fuse cartridge the indicator button, normally retained within a head of the cartridge and adapted to protrude outwardly when the latter has "blown", is disposed axially to the said head and the contact blade corresponding to the latter has a notch formed in its inner transverse edge (the edge connected to the head) in order to define a space which may receive the indicator button. Moreover the lateral sides of the blade have laterally projecting ribs to limit the portion of said blade which may be inserted into the clamp of a cartridge support, thus preventing such a clamp from hindering the protruding movement of the indicator button.

Abstract: The current path of an electric indicating or striker pin fuse, and more particularly its fusible element, includes a point of maximum resistance where fusion of the latter must take place. That predetermined point is arranged in such a way that the pulverulent arc-quenching filler does not impair the proper operation of the indicating or striker pin device.

Abstract: An improved high-voltage fuse, the blown or unblown condition of which can be readily ascertained, is disclosed. Known fuses include a fusible element and a movable component, such as an arcing rod, which is held in a normal first position as long as the fusible element is present and remains intact. When the element fuses and arc is struck, the arcing rod moves through an arc-extinguishing medium to extinguish the arc, coming to rest in a second position. The fusible element, arcing rod, and arc-extinguishing medium are contained within an opaque, insulative housing for the fuse. In the improved fuse, the housing is made of an insulative material which is translucent. The housing's translucency is such that it may be difficult if not impossible to observe the condition of the fuse--blown or unblown--from the fuse's exterior. Accordingly, a member, mounted for movement with the arcing rod, is provided.

Abstract: An electric fuse is of the type including indicating means for indicating if the main fusible element has melted. The indicating means includes a first and second auxiliary fusible element, each having a higher resistance than the main fusible element. When the fuse is fully assembled, and the main fusible element has melted, the path of current is through the first and second auxiliary fusible elements. The second auxiliary fusible element functions to restrain movement of an indicator button. When current flows through the auxiliary fusible elements, the second auxiliary fusible element is designed to melt first, thereby causing the indicator button to move. The operability of the first and second auxiliary fusible elements can be independently and non-destructively determined before and after assembly of the fuse. After fuse assembly, the fuse can be non-destructively disassembled so as to determine the operability of the first and second auxiliary elements.

Abstract: An improved end fitting for a high-voltage fuse is disclosed. The fuse is of the general type having a movable striker pin which resides in a first position as long as a fusible element of the fuse remains intact. Should the fusible element cease to be intact, through fusing thereof or mishandling of the fuse, the striker pin moves to a second position to partially exit beyond an end of the fuse when a sharp end of the striker pin pierces a seal at the fuse end. The improved end fitting is removably mountable to the fuse and includes a body having a bore therethrough. The first end of the body surrounds and encloses the seal. A rod, mounted for movement in the bore at the end of the body, resides in a first normal location when the striker pin is in the first normal position, and in a second location when the striker pin is in the second position.

Abstract: A telephone protector module is provided with indicating means actuated by the actuation of heat sensitive means within the module to provide a visual indication of such actuation externally of the module casing. The indicating means is in the form of an elongated member secured at one end thereof to a moving member of the heat sensitive means. The free end of the indicating member projects through an opening in the end of the casing element, and normally lies flush with the outer surface thereof. Upon actuation of the heat sensitive means, the free end extends outwardly of said surface to be immediately visible to service personnel.

Abstract: A current-limiting power fuse has an indicator mechanism which includes a conductive support cup mounted on one terminal cap and containing an indicator button disposed telescopingly in the cup with an outer hermetically closed end. A spring inside the button biases the outer end face away from the support cup. The outer end of the button is held in place by a fusible indicator wire.The button is a bellows with the inner end hermetically sealed to the bottom of the support cup to isolate the fusible indicator wire from ambient gas.